The present invention relates to a variable speed direct drive drill press/router which utilizes the variable speed high torque characteristics of switched reluctance motors.
A drill press or overhead router generally has the same general configuration. Each includes an upright column supported by a heavy base. Suspended from the column is a table which may be moved up and down and clamped at the desired height. A drill head or housing is mounted on top of the column and supports a driving motor and spindle or spindles above the table. Speed adjustment is generally made by cone pulleys with V-belts that are mounted on the motor and the spindle. These machines provide a means to feed power to the spindle. Such a power feed includes a key way or spline in order to enable the spindle to be moved up or down along its axis, but still retain its drive at any point. A drill chuck at the lower end of the spindle holds a selected drill in position for drilling. By replacing the drill chuck with a collet, a routing tool can be mounted for routing purposes.
Induction motors have typically been used in prior art drill presses and routers. Unfortunately, it is difficult to vary the speed of induction motors and motor torque is also limited, particularly when the speed is reduced. The belts and step pulleys that are used to vary the spindle speed have a range of approximately 300-5000 rpm while the induction motor itself rotates at a constant speed. The belts and step pulleys also multiply the torque of the motor at low spindle speeds.
The variable speed direct drive drill press/router of the present invention employs a switched reluctance motor which eliminates the need for pulleys and belts, while making it very easy to control the speed of the motor and at the same time provide high torque at low speeds. Other features are also available as well apparent from the detailed discussion below.